The mnemonic should match the backup phrase from your hot wallet, obviously keep this secret. The secret can be any GUID and will be used to validate the request came from Monzo, again keep it secret. Finally bws is the URL the bitcore-wallet-client should connect to (we point it at our ScottCoin insance), not necessarily secret.

Now run up the docker image with the configuration file mounted at /app/config.json and publish the port behind some form of HTTPS offload. N.B. HTTPS is required to ensure the secret doesn't become un-secret which would allow someone to plunder your hot wallet funds.

Sign into the Monzo developer console then take the publically accessibly (HTTPS!) URL of the running instance and register it as a webhook.